Seems the test times out in this part of the test :
command: main -Diters=20000 -XX:+UnlockDiagnosticVMOptions -XX:+UnlockExperimentalVMOptions -XX:+UseShenandoahGC -XX:ShenandoahGCMode=generational -XX:TieredStopAtLevel=1 TestReferenceCAS

Example thread stack from a timeout :
----------------------------------------------------------------------------------------
Timeout information:
Running jstack on process 3126290
2025-04-22 22:36:49
Full thread dump OpenJDK 64-Bit Server VM (25-internal-adhoc.jenkinsi.jdk mixed mode, emulated-client, sharing):

Threads class SMR info:
_java_thread_list=0x0000ffff00002610, length=10, elements={
0x0000ffff880bc4e0, 0x0000ffff882e25d0, 0x0000ffff882e3980, 0x0000ffff882e5240,
0x0000ffff882e6fa0, 0x0000ffff882e8b20, 0x0000ffff882ead00, 0x0000ffff883c36e0,
0x0000ffff883ca1b0, 0x0000ffff00000f80
}
_java_thread_list_alloc_cnt=31, _java_thread_list_free_cnt=29, _java_thread_list_max=19, _nested_thread_list_max=0
_tlh_cnt=135, _tlh_times=0, avg_tlh_time=0.00, _tlh_time_max=0
_deleted_thread_cnt=10, _deleted_thread_times=0, avg_deleted_thread_time=0.00, _deleted_thread_time_max=0
_delete_lock_wait_cnt=0, _delete_lock_wait_max=0
_to_delete_list_cnt=0, _to_delete_list_max=1

"main" #3 [3126306] prio=5 os_prio=0 cpu=364.49ms elapsed=1080.60s tid=0x0000ffff880bc4e0 nid=3126306 waiting on condition [0x0000ffff8f1fb000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x0000ffff880bc4e0 [0x2fb422] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked
at sun.nio.fs.UnixFileSystem.<init>(java.base@25-internal/UnixFileSystem.java:93)
at sun.nio.fs.LinuxFileSystem.<init>(java.base@25-internal/LinuxFileSystem.java:45)
at sun.nio.fs.LinuxFileSystemProvider.newFileSystem(java.base@25-internal/LinuxFileSystemProvider.java:46)
at sun.nio.fs.LinuxFileSystemProvider.newFileSystem(java.base@25-internal/LinuxFileSystemProvider.java:39)
at sun.nio.fs.UnixFileSystemProvider.<init>(java.base@25-internal/UnixFileSystemProvider.java:76)
at sun.nio.fs.LinuxFileSystemProvider.<init>(java.base@25-internal/LinuxFileSystemProvider.java:41)
at sun.nio.fs.DefaultFileSystemProvider.<clinit>(java.base@25-internal/DefaultFileSystemProvider.java:35)
at java.util.zip.ZipFile$Source.<clinit>(java.base@25-internal/ZipFile.java:1441)
at java.util.zip.ZipFile$CleanableResource.<init>(java.base@25-internal/ZipFile.java:671)
at java.util.zip.ZipFile.<init>(java.base@25-internal/ZipFile.java:201)
at java.util.zip.ZipFile.<init>(java.base@25-internal/ZipFile.java:148)
at java.util.jar.JarFile.<init>(java.base@25-internal/JarFile.java:333)
at jdk.internal.loader.URLClassPath$JarLoader.getJarFile(java.base@25-internal/URLClassPath.java:682)
at jdk.internal.loader.URLClassPath$JarLoader.ensureOpen(java.base@25-internal/URLClassPath.java:653)
at jdk.internal.loader.URLClassPath$JarLoader.<init>(java.base@25-internal/URLClassPath.java:622)
at jdk.internal.loader.URLClassPath.getLoader(java.base@25-internal/URLClassPath.java:465)
at jdk.internal.loader.URLClassPath.getLoader(java.base@25-internal/URLClassPath.java:409)
- locked <0x00000000fff400b8> (a jdk.internal.loader.URLClassPath)
at jdk.internal.loader.URLClassPath.getResource(java.base@25-internal/URLClassPath.java:331)
at jdk.internal.loader.BuiltinClassLoader.findClassOnClassPathOrNull(java.base@25-internal/BuiltinClassLoader.java:688)
at jdk.internal.loader.BuiltinClassLoader.loadClassOrNull(java.base@25-internal/BuiltinClassLoader.java:620)
- locked <0x00000000fff400b0> (a java.lang.Object)
at jdk.internal.loader.BuiltinClassLoader.loadClass(java.base@25-internal/BuiltinClassLoader.java:578)
at java.lang.ClassLoader.loadClass(java.base@25-internal/ClassLoader.java:490)
at java.lang.Class.forName0(java.base@25-internal/Native Method)
at java.lang.Class.forName(java.base@25-internal/Class.java:547)
at sun.launcher.LauncherHelper.loadMainClass(java.base@25-internal/LauncherHelper.java:861)
at sun.launcher.LauncherHelper.checkAndLoadMain(java.base@25-internal/LauncherHelper.java:746)

"Reference Handler" #28 [3126393] daemon prio=10 os_prio=0 cpu=0.60ms elapsed=1080.22s tid=0x0000ffff882e25d0 nid=3126393 waiting on condition [0x0000ffff6c510000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x0000ffff882e25d0 [0x2fb479] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked
at java.lang.ref.Reference.waitForReferencePendingList(java.base@25-internal/Native Method)
at java.lang.ref.Reference.processPendingReferences(java.base@25-internal/Reference.java:246)
at java.lang.ref.Reference$ReferenceHandler.run(java.base@25-internal/Reference.java:208)

"Finalizer" #29 [3126397] daemon prio=8 os_prio=0 cpu=0.24ms elapsed=1080.21s tid=0x0000ffff882e3980 nid=3126397 in Object.wait() [0x0000ffff6c92b000]
   java.lang.Thread.State: WAITING (on object monitor)
Thread: 0x0000ffff882e3980 [0x2fb47d] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked
at java.lang.Object.wait0(java.base@25-internal/Native Method)
- waiting on <0x00000000fd94b7d0> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.Object.wait(java.base@25-internal/Object.java:389)
at java.lang.Object.wait(java.base@25-internal/Object.java:351)
at java.lang.ref.ReferenceQueue.remove0(java.base@25-internal/ReferenceQueue.java:138)
at java.lang.ref.ReferenceQueue.remove(java.base@25-internal/ReferenceQueue.java:229)
- locked <0x00000000fd94b7d0> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.ref.Finalizer$FinalizerThread.run(java.base@25-internal/Finalizer.java:165)

"Signal Dispatcher" #30 [3126398] daemon prio=9 os_prio=0 cpu=0.75ms elapsed=1080.21s tid=0x0000ffff882e5240 nid=3126398 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x0000ffff882e5240 [0x2fb47e] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked

"Service Thread" #31 [3126399] daemon prio=9 os_prio=0 cpu=22.06ms elapsed=1080.21s tid=0x0000ffff882e6fa0 nid=3126399 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x0000ffff882e6fa0 [0x2fb47f] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked

"Monitor Deflation Thread" #32 [3126400] daemon prio=9 os_prio=0 cpu=109.32ms elapsed=1080.21s tid=0x0000ffff882e8b20 nid=3126400 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x0000ffff882e8b20 [0x2fb480] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked

"C1 CompilerThread0" #33 [3126401] daemon prio=9 os_prio=0 cpu=91.27ms elapsed=1080.21s tid=0x0000ffff882ead00 nid=3126401 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x0000ffff882ead00 [0x2fb481] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked
   No compile task

"Notification Thread" #45 [3126516] daemon prio=9 os_prio=0 cpu=0.13ms elapsed=1079.81s tid=0x0000ffff883c36e0 nid=3126516 runnable [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x0000ffff883c36e0 [0x2fb4f4] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked

"Common-Cleaner" #46 [3126526] daemon prio=8 os_prio=0 cpu=2.20ms elapsed=1079.76s tid=0x0000ffff883ca1b0 nid=3126526 in Object.wait() [0x0000ffff38d47000]
   java.lang.Thread.State: TIMED_WAITING (on object monitor)
Thread: 0x0000ffff883ca1b0 [0x2fb4fe] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked
at java.lang.Object.wait0(java.base@25-internal/Native Method)
- waiting on <0x00000000fff40870> (a java.lang.ref.ReferenceQueue$Lock)
at java.lang.Object.wait(java.base@25-internal/Object.java:389)
at java.lang.ref.ReferenceQueue.remove0(java.base@25-internal/ReferenceQueue.java:124)
at java.lang.ref.ReferenceQueue.remove(java.base@25-internal/ReferenceQueue.java:215)
- locked <0x00000000fff40870> (a java.lang.ref.ReferenceQueue$Lock)
at jdk.internal.ref.CleanerImpl.run(java.base@25-internal/CleanerImpl.java:146)
at java.lang.Thread.runWith(java.base@25-internal/Thread.java:1460)
at java.lang.Thread.run(java.base@25-internal/Thread.java:1447)
at jdk.internal.misc.InnocuousThread.run(java.base@25-internal/InnocuousThread.java:148)

"Attach Listener" #47 [3751618] daemon prio=9 os_prio=0 cpu=2.47ms elapsed=0.15s tid=0x0000ffff00000f80 nid=3751618 waiting on condition [0x0000000000000000]
   java.lang.Thread.State: RUNNABLE
Thread: 0x0000ffff00000f80 [0x393ec2] State: _at_safepoint _at_poll_safepoint 0
   JavaThread state: _thread_blocked

"VM Thread" os_prio=0 cpu=8.55ms elapsed=1080.25s tid=0x0000ffff8829b200 nid=3126382 runnable

"VM Periodic Task Thread" os_prio=0 cpu=2437.32ms elapsed=1080.29s tid=0x0000ffff88193bd0 nid=3126376 waiting on condition

"Shenandoah Regulator Thread" os_prio=0 cpu=2192.59ms elapsed=1080.33s tid=0x0000ffff88183e60 nid=3126366 runnable

"Shenandoah Control Thread" os_prio=0 cpu=12118.92ms elapsed=1080.34s tid=0x0000ffff88182920 nid=3126365 runnable

"Safepoint Cleanup Thread#7" os_prio=0 cpu=0.10ms elapsed=1080.43s tid=0x0000ffff8812fc40 nid=3126349 runnable

"Safepoint Cleanup Thread#6" os_prio=0 cpu=0.06ms elapsed=1080.43s tid=0x0000ffff8812eae0 nid=3126347 runnable

"Safepoint Cleanup Thread#5" os_prio=0 cpu=0.09ms elapsed=1080.45s tid=0x0000ffff8812d980 nid=3126344 runnable

"Safepoint Cleanup Thread#4" os_prio=0 cpu=0.09ms elapsed=1080.47s tid=0x0000ffff8812c820 nid=3126340 runnable

"Safepoint Cleanup Thread#3" os_prio=0 cpu=0.09ms elapsed=1080.48s tid=0x0000ffff8812b6c0 nid=3126337 runnable

"Safepoint Cleanup Thread#2" os_prio=0 cpu=0.09ms elapsed=1080.50s tid=0x0000ffff8812a560 nid=3126334 runnable

"Safepoint Cleanup Thread#1" os_prio=0 cpu=0.10ms elapsed=1080.50s tid=0x0000ffff88129400 nid=3126329 runnable

"Safepoint Cleanup Thread#0" os_prio=0 cpu=0.08ms elapsed=1080.52s tid=0x0000ffff881282a0 nid=3126325 runnable

"Shenandoah GC Threads#7" os_prio=0 cpu=29.28ms elapsed=1080.54s tid=0x0000ffff88127040 nid=3126322 runnable

"Shenandoah GC Threads#6" os_prio=0 cpu=18.11ms elapsed=1080.55s tid=0x0000ffff88125ee0 nid=3126320 runnable

"Shenandoah GC Threads#5" os_prio=0 cpu=13.26ms elapsed=1080.55s tid=0x0000ffff88124d80 nid=3126318 runnable

"Shenandoah GC Threads#4" os_prio=0 cpu=19.59ms elapsed=1080.56s tid=0x0000ffff88123c20 nid=3126314 runnable

"Shenandoah GC Threads#3" os_prio=0 cpu=22.14ms elapsed=1080.57s tid=0x0000ffff88122ac0 nid=3126311 runnable

"Shenandoah GC Threads#2" os_prio=0 cpu=29.13ms elapsed=1080.57s tid=0x0000ffff88121960 nid=3126310 runnable

"Shenandoah GC Threads#1" os_prio=0 cpu=18.66ms elapsed=1080.59s tid=0x0000ffff88120800 nid=3126308 runnable

"Shenandoah GC Threads#0" os_prio=0 cpu=18.06ms elapsed=1080.59s tid=0x0000ffff8811fab0 nid=3126307 runnable

JNI global refs: 14, weak refs: 0

--- Timeout information end.
finished: Tue Apr 22 22:36:49 CEST 2025
elapsed time (seconds): 1080.73